A light-emitting diode (LED) is a semiconductor light source that emits light when current flows through it. When a suitable current is applied to the LED, electrons are able to recombine with electron holes within the LED, releasing energy in the form of photons. This effect is called electroluminescence. The color of the emitted light, which corresponds to the energy of the photon, is determined by the energy band gap of the semiconductor. White light is obtained by using multiple semiconductors or a layer of wavelength converting material on the semiconductor device.
An LED circuit, also referred to as an LED driver, is an electrical circuit used to power the LED by providing a suitable current. The circuit must provide sufficient current to light the LED at the required brightness, but must limit the current to prevent damaging the LED. The balance between sufficient current to power the LED and limiting the current to prevent damage is needed because the voltage drop across the LED is approximately constant over a wide range of operating currents. This causes a small increase in applied voltage to greatly increase the current.
A combination of LEDs is frequently used in a Red-Green-Blue (RGB) color tuning scheme. Adding in the additional LEDs and requirements of powering each LED within the RGB color tuning adds additional complexity to the driving scheme for the RGB LEDs.